Acute airway obstruction by a sheared endotracheal intubation stylet sheath in a premature infant.

Airway obstruction by foreign bodies is rarely encountered in the neonatal intensive care unit. The majority of those cases reported are iatrogenic. This paper reports a case of acute airway obstruction in a preterm infant caused by a sheared plastic sheath of an endotracheal intubation stylet used during tracheal intubation. The small airway of this premature infant posed a challenge to retrieve the foreign body and to ensure adequate gas exchange at the same time. The risks and benefits of available therapeutic options for this rare, but serious complication are reviewed.

Susceptibility to ozone-induced airway inflammation is associated with decreased levels of surfactant protein D.

BACKGROUND: Ozone (O3), a common air pollutant, induces exacerbation of asthma and chronic obstructive pulmonary disease. Pulmonary surfactant protein (SP)-D modulates immune and inflammatory responses in the lung. We have shown previously that SP-D plays a protective role in a mouse model of allergic airway inflammation. Here we studied the role and regulation of SP-D in O3-induced inflammatory changes in the lung. METHODS: To evaluate the effects of O3 exposure in mouse strains with genetically different expression levels of SP-D we exposed Balb/c, C57BL/6 and SP-D knockout mice to O3 or air. BAL cellular and cytokine content and SP-D levels were evaluated and compared between the different strains. The kinetics of SP-D production and inflammatory parameters were studied at 0, 2, 6, 12, 24, 48, and 72 hrs after O3 exposure. The effect of IL-6, an O3-inducible cytokine, on the expression of SP-D was investigated in vitro using a primary alveolar type II cell culture. RESULTS: Ozone-exposed Balb/c mice demonstrated significantly enhanced acute inflammatory changes including recruitment of inflammatory cells and release of KC and IL-12p70 when compared with age- and sex-matched C57BL/6 mice. On the other hand, C57BL/6 mice had significantly higher levels of SP-D and released more IL-10 and IL-6. Increase in SP-D production coincided with the resolution of inflammatory changes. Mice deficient in SP-D had significantly higher numbers of inflammatory cells when compared to controls supporting the notion that SP-D has an anti-inflammatory function in our model of O3 exposure. IL-6, which was highly up-regulated in O3 exposed mice, was capable of inducing the expression of SP-D in vitro in a dose dependent manner. CONCLUSION: Our data suggest that IL-6 contributes to the up-regulation of SP-D after acute O3 exposure and elevation of SP-D in the lung is associated with the resolution of inflammation. Absence or low levels of SP-D predispose to enhanced inflammatory changes following acute oxidative stress.

Analysis of binding and membrane destabilization of phospholipid membranes by surfactant apoprotein B.

To further elucidate the nature of the molecular interactions of surfactant apoprotein B (SP-B) with phospholipid (PL) membranes, we studied the binding of SP-B to PL membranes and the lipid-dependency of its subsequent effects on leakage and fusion of membranes. SP-B binding to membranes was studied by labeling the protein with the fluorophore 7-nitro-2,1,3-benzoxadiazol-4-yl (NBD) and measuring the fluorescence of the labeled protein in the presence of varying amounts of dipalmitoylphosphatidylcholine-egg phosphatidylglycerol (DPPC-eggPG; 7-3). Leakage of contents from liposomes made of DPPC and varying molar fraction of egg phosphatidylcholine (eggPC) or eggPG was assessed by measuring the fluorescence of entrapped water-soluble probes ANTS and DPX. Fusion of membranes was assessed by measuring the fluorescence of membrane-bound NBD-phosphatidylethanolamine (NBD-PE) and rhodamine-PE (RHO-PE). We found that SP-B bound to PL membranes with high affinity and appeared to irreversibly cluster at the membrane surface, leading to graded release of the vesicle contents and eventually fusion of the membranes with increasing protein-lipid ratios. All lipid mixtures tested were susceptible to the membrane disruptive effects of SP-B, but DPPC-eggPG membranes displayed a biphasic response to increasing molar fractions of eggPG, whereas increasing fractions of eggPC elicited a monotonic response.

Kinetics of phospholipid membrane fusion induced by surfactant apoproteins A and B.

Surfactant apoproteins A (SP-A) and B(SP-B) interact with the lipids of surfactant and such protein- lipid interactions may be of importance in several of the steps in the surfactant cycle. We analyzed the kinetics of fusion of dipalmitoylphosphatidylcholine-phosphatidyglycerol (DPPC:PG; 7:3, w/w) phospholipid vesicles induced by SP-B alone, in the presence of 5 mM calcium, and in the presence of calcium and SP-A. Membrane fusion was measured by the method of resonance energy transfer between non-exchangeable fluorophores incorporated in the membrane. Data were analyzed using a mass action kinetic model for membrane fusion between phospholipid vesicles. We found a SP-B dose-dependent increase in lipid mixing within a range of phospholipid concentration of 5 to 100 micromolar. Calcium caused a small additive increase in lipid mixing, but calcium and SP-A combined markedly increased lipid mixing induced by SP-B. Both aggregation and fusion rate constants increased with an increase in the SP-B/lipid ratio. In the presence of calcium and SP-A, the number of vesicles per fusion product markedly increased, as did the aggregation rate constants, whereas the fusion rate constants remained essentially unchanged.

Biosynthesis of granulysin, a novel cytolytic molecule.

Granulysin is a newly described lytic molecule expressed by CTL and NK cells. Three mRNA (519, 520, and 522) and two protein products of 15 and 9 kDa are encoded by the granulysin gene. Stable transfectants overexpressing the predominate 520 mRNA were generated to determine the protein products originating from the translation of this message. A transfectant of the NK cell tumor YT overexpressed both 15 and 9 kDa proteins while a transfectant of the T cell tumor HuT78 produced mainly 15 kDa granulysin. Thus the 520 mRNA is sufficient for production of both 15 and 9 kDa granulysin. 9 kDa granulysin accumulated via post-translational processing of 15 kDa protein and was present intracellularly but not in the cell culture supernatant, indicating specific retention of the 9 kDa protein. An inhibitor of granule acidification, concanamycin A, blocked the processing of 15 kDa granulysin to the 9 kDa form. A deduced structural difference between the two forms of the protein and a decrease in lytic activity of 9 kDa granulysin at granule pH suggest two mechanisms by which a granulysin expressing cell is protected from autolysis during the biosynthesis of this potentially harmful molecule.

Lung overexpansion increases pulmonary microvascular protein permeability in young lambs.

To study the effects of inflation pressure and tidal volume (VT) on protein permeability in the neonatal pulmonary microcirculation, we measured lung vascular pressures, blood flow, lymph flow (QL), and concentrations of protein in lymph (L) and plasma (P) of 22 chronically catheterized lambs that received mechanical ventilation at various peak inflation pressures (PIP) and VT. Nine lambs were ventilated initially with a PIP of 19 +/- 1 cmH2O and a VT of 10 +/- 1 ml/kg for 2-4 h (base line), after which we overexpanded their lungs with a PIP of 58 +/- 3 cmH2O and a VT of 48 +/- 4 ml/kg for 4-8 h. QL increased from 2.1 +/- 0.4 to 13.9 +/- 5.0 ml/h. L/P did not change, but the ratio of albumin to globulin in lymph relative to the same ratio in plasma decreased, indicating altered protein sieving in the pulmonary microcirculation. Seven other lambs were mechanically ventilated for 2-4 h at a PIP of 34 +/- 1 cmH2O and a VT of 23 +/- 2 ml/kg (base line), after which their chest and abdomen were bound so that PIP increased to 54 +/- 1 cmH2O for 4-6 h without a change in VT. QL decreased on average from 2.8 +/- 0.6 to 1.9 +/- 0.3 ml/h (P = 0.08), and L/P was unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased pulmonary vascular filtration pressure does not alter lung liquid secretion in fetal sheep.

The purpose of this study was to determine whether an increase in pulmonary vascular filtration pressure affects net production of liquid within the lumen of the fetal lung. We studied 14 chronically catheterized fetal lambs [130 +/- 3 (SD) days gestation] before, during, and after a 4-h rapid (500 ml/h) intravenous infusion of isotonic saline. In seven fetuses we measured pulmonary arterial and left atrial pressures, lung lymph flow, and protein osmotic pressures in plasma and lymph. In eight lambs with a chronically implanted tracheal loop cannula, we measured the change in luminal lung liquid volume over time by progressive dilution of tracheally instilled 125I-albumin, which stays within the lung lumen. Saline infusion increased pulmonary vascular pressures by 2-3 mmHg and decreased the plasma-lymph difference in protein osmotic pressure by 1 mmHg. Lung lymph flow increased from 1.9 +/- 0.6 to 3.9 +/- 1.2 (SD) ml/h; net production of luminal lung liquid did not change (12 +/- 5 to 12 +/- 6 ml/h). Thus an increase in net fluid filtration pressure in the pulmonary circulation, which was sufficient to double lung lymph flow, had no significant effect on luminal lung liquid secretion in fetal sheep.

Hypoproteinemia slows lung liquid clearance in young lambs.

To determine whether hypoproteinemia slows the rate at which liquid is cleared from the lung lumen, we studied 36 lambs, 18 of which underwent repeated plasmapheresis, reducing plasma protein concentration by 37% and plasma protein osmotic pressure by 39%. We killed 29 lambs (14 hypoproteinemic and 15 normoproteinemic) and removed their lungs 1, 2, or 6 h after intratracheal instillation of isotonic saline (6 ml/kg body wt). We measured extravascular lung water and determined the percentage of tracheally instilled liquid that was cleared from the lungs by comparison with control lambs that did not receive saline into their airways. The percent liquid cleared from the lungs after 1 and 2 h was significantly less in hypoproteinemic than in normoproteinemic lambs (37 vs. 65% at 1 h, 58 vs. 75% at 2 h, respectively). By 6 h nearly all the liquid (> 92%) was cleared from the lungs of all lambs. Thus hypoproteinemia slows the initial rate of clearance of liquid from the lungs of lambs. To determine whether reduced plasma protein osmotic pressure might redirect this liquid into lung lymphatics, we measured lung lymph flow (Q1) in five lambs (7.7 +/- 1.4 kg, 19 +/- 4 days old) for > or = 2 h before and 6 h after tracheal instillation of saline. In each lamb, paired studies were done 3-6 days apart; between studies the lambs underwent plasmapheresis.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in lung lipid during spontaneous labor in fetal sheep.

The goals of this study were 1) to examine changes in lung liquid formation and composition during spontaneous labor in fetal lambs and 2) to determine the importance of beta-adrenergic stimulation and transepithelial Na+ flux in removing liquid from the lung lumen near birth. We measured net production of lung liquid (Jv), lung liquid composition, and transpulmonary electrical potential difference (PD) before and during labor in fetal sheep with chronically implanted tracheal and vascular catheters. We determined Jv by measuring rate of change in lung liquid concentration of 125I-albumin, an impermeant tracer that was mixed in lung liquid at the start of each study. In 17 paired experiments, Jv decreased from 11 +/- 2 ml/h (Jv > 0 = secretion) before labor to -1 +/- 2 ml/h (Jv < 0 = absorption) during labor; in 5 paired experiments, PD changed from -7 +/- 1 mV (lumen negative) before labor to -12 +/- 1 mV during labor. To determine whether absorption of lung liquid during labor is the result of beta-adrenergic stimulation, we studied the effect of propranolol on Jv during labor. When propranolol (40 microM) was added to lung liquid during active labor, Jv decreased from -2 +/- 2 to -8 +/- 3 ml/h (n = 9). Thus, propranolol did not inhibit lung liquid absorption during labor. To determine whether transepithelial Na+ movement provides the driving force for lung liquid clearance during labor, we tested the effects of amiloride, an Na+ transport inhibitor, on Jv and PD.(ABSTRACT TRUNCATED AT 250 WORDS)

Congenital diaphragmatic hernia associated with a gastroesophageal duplication cyst: a case report.

Severe left congenital diaphragmatic hernia was diagnosed in a baby prenatally, and she underwent hernia repair on the sixth postnatal day of life. She was found to have a huge symptomatic gastroesophageal duplication cyst on day 24 of life. A thoracoabdominal dissection allowed successful cyst excision. J Pediatr Surg 36:626-628.

The pulmonary collectins and surfactant metabolism.

Lung surfactant covers and stabilizes a large, delicate surface at the interface between the host and the environment. The surfactant system is placed at risk by a number of environmental challenges such as inflammation, infection, or oxidant stress, and perhaps not surprisingly, it demonstrates adaptive changes in metabolism in response to alterations in the alveolar microenvironment. Recent experiments have shown that certain components of the surfactant system are active participants in the regulation of the alveolar response to a wide variety of environmental challenges. These components are capable not only of maintaining a low interfacial surface tension but also of amplifying or dampening inflammatory responses. These observations suggest that regulatory molecules are capable of both sensing the environment of the alveolus and providing feedback to the cells regulating surfactant synthesis, secretion, alveolar conversion, and clearance. In this review we examine the evidence from in vitro systems and gene-targeted mice that two surfactant-associated collectins (SP-A and SP-D) may serve in these roles and help modify surfactant homeostasis as part of a coordinated host response to environmental challenges.

Pulmonary surfactant therapy.

Surfactant replacement therapy is now an integral part of the care of neonates since several clinical trials of natural surfactant extracts and synthetic preparations have shown efficacy in the treatment of infants with hyaline membrane disease. In these studies, early treatment with exogenous surfactant substantially reduced mortality and the incidence of air leak, although it did not appear to reduce the incidence of other complications, in particular bronchopulmonary dysplasia. Early reports of exogenous surfactant therapy in patients with the adult respiratory distress syndrome, although promising, remain limited in number. More research is needed to improve on current modes of therapy and to investigate the possible role of surfactant in other lung diseases of both newborns and adults.

Urinary effects of morphine in preterm infants.

AIM: To describe the association between morphine administration in preterm infants, hydronephrosis, and renal dysfunction. METHODS: The findings were based on serial ultrasound examinations and blood studies. RESULTS: Two preterm infants had bladder distension and hydronephrosis after they received intravenous morphine for analgesia. Morphine was used at a low dose. Each patient had a normal urine output and normal serum creatinine before the signs and symptoms of urinary retention were observed. Within 24 h of morphine administration, each infant concurrently developed oliguria and elevation of the serum creatinine. Cessation of morphine and urinary drainage resulted in rapid and complete resolution of the hydronephrosis and the elevated creatinine. CONCLUSION: Morphine, even at low dosages, can be associated with hydronephrosis in hospitalized preterm infants.

Effects of surfactant apolipoproteins on liposome structure: implications for tubular myelin formation.

Tubular myelin is one of several forms of lung surfactant and may play an important role in its surface activity. To determine possible mechanisms of tubular myelin formation, we studied the effects of purified surfactant proteins (SP-A, SP-B, and SP-C) on large unilamellar dipalmitoylphosphatidylcholine-egg phosphatidylglycerol (7/3; wt/wt) liposomes. We studied different types of membrane interaction induced by the apolipoproteins and correlated these with the observed changes in ultrastructure. Aggregation was assessed by measurement of light absorbance, lysis, and fusion by measurement of the fluorescence emitted by water-soluble and lipid-soluble probes, respectively. Mixtures of the apolipoproteins and liposomes were examined in ultrastructural studies by negative staining and by thin sectioning. We found that each protein had a pronounced and distinct effect on liposome structure. SP-A caused aggregation, whereas SP-B and SP-C also caused extensive leakage of liposome contents (lysis) and some degree of lipid mixing (fusion). The disruptive effects of SP-B and to a lesser extent those of SP-C were correlated by negative staining with the appearance of bilayer disks, which tended to aggregate into large sheets. There was a marked synergy between SP-A and SP-B in the process of membrane fusion in the presence of calcium, which correlated with an early (10 min) and extensive rearrangement of the structures seen by electron microscopy followed by a delayed (24 h) appearance of small amounts of tubular myelin.

GM-CSF mediates alveolar macrophage proliferation and type II cell hypertrophy in SP-D gene-targeted mice.

Mice deficient in surfactant protein (SP) D develop increased surfactant pool sizes and dramatic changes in alveolar macrophages and type II cells. To test the hypothesis that granulocyte-macrophage colony-stimulating factor (GM-CSF) mediates alveolar macrophage proliferation and activation and the type II cell hypertrophy seen in SP-D null mice, we bred SP-D and GM-CSF gene-targeted mice to obtain littermate double null, single null, and wild-type mice. Bronchoalveolar lavage levels of phospholipid, protein, SP-D, SP-A, and GM-CSF were measured from 1 to 4 mo. There was an approximately additive accumulation of phospholipid, total protein, and SP-A at each time point. Microscopy showed normal macrophage number and morphology in GM-CSF null mice, numerous giant foamy macrophages and hypertrophic type II cells in SP-D null mice, and large but not foamy macrophages and mostly normal type II cells in double null mice. These results suggest that the mechanisms underlying the alveolar surfactant accumulation in the SP-D-deficient and GM-CSF-deficient mice are different and that GM-CSF mediates some of the macrophage and type II cell changes seen in SP-D null mice.

Ion transport regulation of lung liquid secretion in foetal lambs.

To test the hypothesis that liquid formation in the foetal lung reflects the balance between Cl- secretion and Na+ absorption by the respiratory tract epithelium, we studied the independent and combined effects of selective ion transport inhibitors on basal production of lung liquid in foetal lambs. We prepared 19 foetal lambs (gestation 125 +/- 4, term = 147 days) with chronic indwelling catheters for subsequent measurement of luminal liquid production over time (JV). Using an impermeant tracer technique, we measured JV before and after tracheal instillation of 2 different inhibitors of ion transport: bumetanide, a Na(+)-K(+)-2Cl- co-transport inhibitor, and amiloride, a Na+ transport inhibitor. In 7 foetuses we sequentially added bumetanide (10(-4) M) and 2 different concentrations of amiloride (10(-6) M, 10(-4) M) to the liquid within the lung lumen. After we gave bumetanide, JV decreased from 12 +/- 4 ml/h to 0 +/- 5 ml/h and subsequently increased during the 2 periods of amiloride exposure (10(-6) M: 6 +/- 5 ml/h; 10(-4) M: 7 +/- 7 ml/h). In 5 control studies we gave bumetanide, followed by only amiloride vehicle. JV for all time periods in the control studies was similar to the experimental group, demonstrating no effect of amiloride. In 5 foetuses we administered the 2 concentrations of amiloride before bumetanide. There was no change in JV with either concentration of amiloride (baseline: 13 +/- 2 ml/h; 10(-6) M amiloride: 15 +/- 5 ml/h; 10(-4) M amiloride: 13 +/- 6 ml/h).(ABSTRACT TRUNCATED AT 250 WORDS)

Vasopressin effects on lung liquid volume in fetal sheep.

The normal switch from placental to pulmonary gas exchange at birth requires rapid removal of liquid from the lungs. Previous reports contend that vasopressin may be important in regulating this process, but this notion derives from studies in which fetal sheep received very large doses of vasopressin that yielded plasma concentrations at least 10 times greater than those that have been measured during normal labor. To study the physiologic effects of vasopressin on lung liquid volume in fetal sheep, we made three sets of experiments. First, we measured plasma vasopressin concentrations [VP] in 15 late-gestation fetal sheep, five of which were at various stages of spontaneous labor. [VP] in these fetuses ranged from < 1 (prelabor) to 31 (during labor) microU/mL; postmortem extravascular lung water (EVLW) ranged from 4.5 to 14.5 g/g dry lung tissue. In a second series of studies, we measured EVLW in five sets of near-term (138 +/- 1 d, term = 147 d) twin fetal sheep that received an 8-h i.v. infusion of either isotonic saline (control twin) or AVP (AVP-treated twin) at a rate of approximately 1 (mU/kg)/min. This dose was chosen to mimic [VP] measured in fetuses that had been studied during labor. [VP] did not change in the control twins, whereas [VP] increased from 1.8 +/- 1.0 to 27.7 +/- 3.5 microU/mL in treated twins. There was a small, statistically significant difference in EVLW between twins that received AVP and untreated twins (11.9 +/- 1.8 versus 14.6 +/- 2.8 g/g dry lung).(ABSTRACT TRUNCATED AT 250 WORDS)

Intrapulmonary terbutaline and aminophylline decrease lung liquid in fetal lambs.

To see if phosphodiesterase inhibition might enhance the effect of beta-adrenergic stimulation on fetal lung liquid secretion, we studied the independent and combined effects of intrapulmonary terbutaline and aminophylline on net production of lung luminal liquid over time (Jv) in fetal lambs with chronically placed tracheal loop catheters. We calculated Jv during baseline and experimental periods (90-120 min each) by measuring serial concentrations of 125I-albumin, an impermeant tracer that was well mixed in the luminal liquid. In 21 experiments, tracheal instillation of terbutaline (10(-5) M) decreased Jv from 11 +/- 1 (mean +/- SEM) to -3 +/- 2 mL/h. In six other studies, aminophylline (10(-3) M) alone had no significant effect on Jv. In 12 experiments, we gave the two drugs sequentially: terbutaline decreased Jv from 11 +/- 2 to -3 +/- 2 mL/h and aminophylline further decreased Jv to -8 +/- 2 mL/h. Amiloride (10(-4) M), an inhibitor of epithelial Na+ transport, reversed the combined effect of terbutaline and aminophylline, increasing Jv to 8 +/- 1 mL/h. Thus, phosphodiesterase inhibition enhances the beta-adrenergic effect of terbutaline on Na(+)-dependent absorption of liquid from the lung lumen of fetal lambs.

Ultrastructure of phospholipid mixtures reconstituted with surfactant proteins B and D.

Surfactant protein (SP)-D is secreted from pulmonary alveolar type II cells into the alveolar lumen where potential interactions with surfactant lipids might occur. SP-D binds phosphatidylinositol (PI), a component of mammalian surfactants that is increased in a variety of injury states. We investigated the ultrastructure and properties of lipid protein recombinants that included SP-D, PI, and SP-B and compared these with recombinants based on SP-A. SP-D had a profound effect on the organization of phospholipid vesicles containing PI and SP-B, promoting the formation of atypical but highly ordered and surface-active tubular aggregates distinct in their dimensions and shape from the classical tubular myelin formed by SP-A. We also found both types of tubules in the secretions of type II cells maintained in long-term culture. These results suggest that surface atypical tubules can be formed with SP-D in vitro and in vivo.